Images are formed in silver halide color photographic materials by reaction between oxidized silver halide developing agent and a dye forming compound known as a coupler. It has become common practice to modify the photographic properties of the image, such as sharpness, granularity, contrast and color reproduction, by the use of an image modifying compound commonly referred to as a development inhibitor releasing (DIR) compound. Such materials were first described in U.S. Pat. Nos. 3,148,062 and 3,227,554.
In addition to development inhibitors, other photographically active groups may desirably be released during photographic processing. Such groups include development accelerators, bleach accelerators, bleach inhibitors, complexing agents, toners, stabilizers, etc.
Photograpically active groups typically are released during the development step in an imagewise manner. On occasion, depending upon the particular photographically active group and the purpose it is to serve, it may be desired to make available the active form of the photographically active group at a stage in the processing of the photographic element other than the development step, or in a uniform manner, or both.
Many release compounds release the photographically active group directly in its active form. This limits the use of such compounds in those situations where it is desired that the photographically active group act at a location remote from that where it is released. This is alleviated somewhat by release compounds in which the photographically active group is blocked by and released from an intervening group, commonly called a timing group, after that group is released from the carrier portion of the compound. Compounds of this type are described in U.S. Pat. Nos. 4,248,962; 4,409,323; 4,684,604; 5,034,311 and 5,055,385 and in European patent application 0 167 168.
The use of a timing group that blocks the active function of the photographically active group permits the photographically active group to diffuse away from the site where it is initially released before it is made available in the active form by removal of the blocking group. However, this still does not provide complete control over the location where the photographically active group acts. The use in a photographic element of a compound having a photographically active group in which the active site is blocked is known. For example, U.S. Pat. Nos. 4,343,893 and 4,690,885, and European Published Patent Application 0 335 319 show such compounds. However, in this type of compound the blocking group is removed during processing in a non-imagewise fashion. Thus, there is no correlation between release and imaging.
German Published Patent Application DT OS 35 06 805 describes the release of a photographically active group during photographic processing followed by modification of the photographic effect of that group by another compound released during processing, either to strengthen or weaken the effect of the originally released photographically active group. The active site of the photographically active group is present upon original release. The mechanisms and reactions which are described in this patent application for the release of photographically active groups are substantially different from those employed in the present invention for releasing dye moieties.
The use of masking couplers to correct for the unwanted absorption of image dyes is well known in the art. The masking effect is generated by the imagewise destruction of a dye which has the same hue as the unwanted absorption for which it corrects. The loss of density due to the destruction of the masking coupler offsets the unwanted gain in density due to the unwanted absorptions of the image dye in color records other than the primary color record of the image dye.
Masking couplers known in the art utilize dyes attached to the coupling site of a coupler parent. Coupling of the masking coupler with an imagewise distribution of oxidized developer causes a decrease in dye density as a result of the destruction of the dye chromophore or the release and subsequent wash out of the hydrophilic dye moiety.
In Mooberry, et al., U.S. Pat. No. 4,840,884, imagewise release of a shifted dye moiety is followed by unshifting to generate a dye of desired hue. The shifted dye is attached to the coupling site of the coupler parent, either directly or via a linking group, and is released imagewise upon reaction with oxidized developer. Unlike masking couplers, the shifted dyes are retained in the element after release.
The use of uniform distributions of filter dyes in photographic elements is also well known in the art for adjusting the spectral composition of light during exposure. Most filter dyes are removed during photographic processing. However, the removal of such dyes is typically in a non-imagewise manner.
It would be desirable to provide photographic elements in which a dye is released only after it has interacted with a nucleophile which has been released in an imagewise manner, so that the release of the dye is a function of the presence of the nucleophile. This would provide the ability to compensate for unwanted absorptions of certain image dyes, and the ability to increase color density in a given color record of a photographic element.